I feel like the 1MB limit is excessively generous, especially for text-only pages. But maybe that's what makes it so damning when pages fail to adhere to it. I know at least one website I maintain fails it spectacularly (though in my defense it's entirely because of that website being chock-full of photos, and full-res ones at that; pages without those are well under that 1MB mark), while other sites I've built consist entirely of pages within a fraction of that limit.
It'd be interesting to impose a stricter limitation to the 1MB Club: one where all pages on a given site are within that limit. This would disqualify Craigslist, for example (the listing search pages blow that limit out of the water, and the listings themselves sometimes do, too).
I also wonder how many sites 1mb.club would have to show on one page before it, too, ends up disqualifying itself. Might be worthwhile to start thinking about site categories sooner rather than later if everyone and their mothers starts spamming that GitHub issues page with sites (like I'm doing right now).